In chemical analysis, matrix refers to the components of a sample other than the analyte[1] of interest.
[2] For example, the ionic strength of the solution can have an effect on the activity coefficients of the analytes.
[5] In cases with complex or unknown matrices, the standard addition method can be used.
[3] In this technique, the response of the sample is measured and recorded, for example, using an electrode selective for the analyte.
Matrix enhancement and suppression is frequently observed in modern analytical routines, such as GC, HPLC, and ICP.